The present invention relates to a novel method and apparatus for regenerating the water softening or conditioning material in an automatic water softener.
Water softening with ion exchange material such as resin particles or the like is well known in the art. During the softening process, or service cycle, the ion exchange resin particles acquire hardness inducing ions from the water in exchange for soft ions, or ions which do not induce hardness. After prolonged contact of the resin particles with raw water, their ion exchange capacity is diminished considerably and periodic regeneration of the resin particles must be accomplished, conventionally by contacting the resin particles with a brine solution, i.e., an aqueous solution of sodium chloride or potassium chloride or the like.
The ion exchange process and the regeneration of the ion exchange material are accomplished in a softener or resin tank of well known construction, while a separate brine tank is conventionally employed to manufacture brine for use during the regeneration cycle. When regeneration is initiated in the system, brine is drawn from the brine tank and passed through the bed of ion exchange material in the softener tank to reverse the exchange of ions and revitalize the bed by removing hardness inducing ions and replacing them with sodium ions, for example, from the brine solution.
The precise amount of brine which is required to regenerate a bed of ion exchange materials of predetermined volume, is dependent uon the extent to which the bed is exhausted during the service cycle. This, in turn, is dependent upon a number of factors, including: (1) the extent of hardness of the water being treated; and (2) the quantity of water treated during a service cycle. In order to enhance the economy of the system, it is desirable to precisely limit the amount of salt utilized in each regeneration cycle and the frequency of each regeneration cycle to the amount required.
Most water softeners are designed to regenerate on a predetermined timed cycle determined by taking into consideration the above-mentioned factors. Because of this, if a water softening system is subjected to either an abnormally high or low usage during a particular period of time, the water softening system will still regenerate itself during the predetermined regeneration cycle. In the instance of abnormally low usage, a waste of salt and water results, and in the instance of abnormally high usage, the water softening system is unable to adequately soften all of the water passing through the system.
There have been many proposed systems to solve the above mentioned problem. Such systems have been based upon utilizing means to detect the state of exhaustion of the resin bed or utilizing means to measure the quantity of water which has passed through the resin bed since the previous regeneration.
Examples of heretofore used systems which attempt to detect the state of exhaustion of the resin bed are disclosed in U.S. Pat. Nos. 3,246,759 and 4,257,887. These systems have a plurality of spaced electrode probes mounted in the resin bed to detect the condition of the resin bed, and when the condition is such that rejuvenation should occur, a control circuit is activated to command regeneration. These systems rely on the difference in conductivity of exhausted and rejuvenated resin particles. These systems have proved to be generally unreliable in operation, relatively expensive, and the salt usage is not always in direct proportion to the volume of soft water produced.
One example of a system which utilizes a means to measure the quantity of water which has passed through the bed is disclosed in U.S. Pat. No. 3,687,289. This system includes a metering device associated with the soft water line to meter a predetermined proportion of water from the soft water line. The metered water is directed to a chamber having an adjustable water storage capacity. The proportion of water metered from the soft water line is directly proportional to the storage capacity of a pump chamber. The water stored in the chamber is periodically directed to the brine storage tank. The brine storage tank includes means to activate a timer to signal the need for regeneration when the water level in the brine tank reaches a predetermined level. The proportion of water metered into the brine tank is adjusted dependent upon the hardness of the water being treated.
The above discussed water softener systems signal a regeneration as usage proceeds through an allocated amount of soft water. However, the actual time of regeneration is usually delayed to occur at night as is the custom. Therefore, a reserve capacity in the resin bed is required to provide soft water for the remaining portion of the day after the signal point is reached. The reserve point is typically selected to correspond with the point when approximately 70% of the capacity of the resin bed is reached. This large reserve is needed to maintain soft water service in the event that the signal point is reached early in the day. Although such water softener systems may be designed or adjusted to vary the reserve capacity of the resin bed, they will repeat thereafter with a fixed reserve capacity.
With the advent of micro-computer technology, a water softener system was recently designed which utilizes a micro-computer to adjust the reserve capacity from day to day in response to the usage encountered. The system includes a water meter turbine which determines the quantity of water passing through the resin bed. The micro-computer calculates the percentage of the capacity of the resin bed used since the last regeneration based upon the quantity and hardness of the water which has passed through the resin bed. The micro-computer employs an algorithm to make its calculations and decisions as time and water use accumulates. The algorithm allows a large reserve on early days following a regeneration and continues to reduce the amount of reserve capacity as more days of significant water usage go by since the last previous regeneration. At such time as the reserve capacity for that day is reached, the water softener is scheduled for regeneration that night and is regenerated with a preselected fixed quantity of salt.
A similar system to the system described immediately hereinabove utilizes a similar algorithm with additional criteria for reducing the probability of overrunning the variable reserve. This system determines and stores water usage averages for each particular day of the week. At the end of each day the calculated remaining reserve capacity in the resin bed is determined and compared with the stored water usage average for the next day. If the remaining reserve capacity is not adequate to meet the expected demands of the next day, the water softener is scheduled for regeneration that night with a preselected fixed quantity of salt.
The above described micro-computer systems utilize a variable reserve capacity and are able to schedule regenerations more in proportion to water usage and thereby reduce the reserve capacity of the resin bed at the time of regeneration more accurately than in prior systems. However, in both of these systems, a fixed quantity of salt is utilized during each regeneration. The quantity of brine solution which is directed through the resin bed is the same during each regeneration. Accordingly, in instances when the reserve capacity of the resin bed is relatively high at the time of regeneration, an excess quantity of salt is passed through the bed than is necessary to fully rejuvenate the resin particles in the bed. This results in a waste of salt.